Screw-type fasteners are available that limit the torque that can be applied to the fastener by a fastening tool such as a screwdriver or socket drive. Excessive torque may damage the fastener itself or may damage the objects fastened together by the fastener. If the fastener itself is damaged, it may be difficult to unloosen and remove later.
In one known type of torque-limited fastener, the fastener has component parts that shear off and separate from the remainder of the fastener when a drive tool applies a limiting torque. The component parts are also used for loosening the fastener, so it may be difficult or impossible to remove the fastener after the component parts are sheared off.
Other known types of torque-limited fasteners incorporate separate, multi-part mechanical components that slip relative to one another when a drive tool applies a limiting torque to the fastener. Although these fasteners can be later loosened after fastening, the fasteners are expensive and the component assemblies prone to failure such that the applied torque exceeds the desired limiting torque.
Thus there is a need for a reliable torque-limited fastener that limits the torque that can be applied to the fastener and yet can be loosened and removed after fastening. The fastener is preferably an integral-one piece member so that costs associated with a multi-part assembly are eliminated. In possible embodiments, the fastener should not include component parts that shear off and separate from the remainder of the fastener for use in environments where such loose parts should be avoided.